Final answer:
To find the aircraft's final position relative to Dallas after flying 400 km North and then 130 km South, calculate the net displacement which is 270 km North of Dallas.
Step-by-step explanation:
The plane's final position relative to Dallas can be determined by calculating the net displacement of the aircraft. The aircraft first flies 400 km North from Dallas, and after refueling, it flies 130 km South. The net displacement is the difference between these two distances in a straight line, which is 400 km - 130 km.
The result is a net displacement of 270 km North of Dallas. This means that, after completing its journey, the aircraft is situated 270 kilometers to the North of Dallas.